Electrostatic treatment of oil and water has been used by the oil industry for many years to aid in the separation of water from an oil-continuous stream. Treating a water-in-oil emulsion by passing it through a high voltage electrostatic field has been shown to promote rapid coalescence of the water droplets leading to rapid separation. However, this method has traditionally been limited to water contents in the oil up to only about 20%. Electrostatic voltage sources include AC, DC and combined AC/DC. Attempts to increase the allowable inlet water content have been limited due to the electrically conductive nature of high water content emulsions.
An electrostatic method developed by Dr. Philip Bailes and Steve Larkai of the University of Bradford has proven to successfully treat emulsions with water contents as high as 70% or more. The emulsion must remain oil-continuous with the water finely dispersed throughout. The Bailes/Larkai coalescer solves the high conductivity problem by using two methods, namely an insulated electrode and a pulsed DC voltage field. However, standard vessel designs as commonly used in industry have proven unsatisfactory for the purpose of treating high water content oilfield emulsions operating at high pressures.
For additional background information relating to the basic subject matter of this invention, reference may be had to U.S. Pat. Nos. 4,601,834 and 4,747,921, both of which patents are incorporated herein by reference.